The present invention relates to a method and a device for analyzing and quantifying flows, especially for the three-dimensional determination of flow velocity components or the three-dimensional visualization of flows in fluids or gases.
German Patent No. 199 63 393 concerns a method and a device for the three-dimensional determination of flow velocities in fluids or gases, whereby electromagnetic waves may be detected having been at least partially emitted or scattered from particles contained in a detection space and that may characterize the flow. For this purpose, in temporal succession, at least two approximately parallel light planes, arranged spatially one behind the other, may be generated using electromagnetic waves of a different frequency or a different frequency spectrum, the detection space being scanned by the waves. In addition, it was also proposed in that document, to record in a frequency-selective manner or a frequency-band-selective manner two-dimensional, especially color images of the scanned area of the detection space using a detection device, e.g. a CCD color camera.
It is an objective of the exemplary embodiment and/or exemplary method of the present invention to develop an alternative method and device that may be suitable for carrying out the method of German Patent No. 199 63 393.
The exemplary embodiment and/or exemplary method of the present invention may have the advantage of a reduced apparatus cost, and one less susceptible to fluctuations, in the area of the illumination device, while at the same time maintaining the advantages of the method of German Patent No. 199 63 393. For example, the data sets arising in the exemplary embodiment and/or exemplary method according to the present invention may be relatively small and therefore may be processed and evaluated easily and clearly. In addition, color modulation of the incident light beam or laser beam may be dispensed with, for example, using an acousto-optical modulator, by undertaking the color coding of the received two-dimensional images on the receiving side, i.e., in the area of the image detector.
Finally, the exemplary embodiment and/or exemplary method according to the present invention may have the advantage that, in comparison, for example, to methods which use high-speed camera systems, significantly reduced scattered light intensities may be sufficient.
Advantageously, there may be a multiplicity of possibilities to change, as a function of time, the frequency spectrum in response to scanning the detection space detected by the image detector(s) or the frequency detected by the image detector(s) or the intensity detected by them. In this context, it may be especially advantageous if, as the image detector, a CCD camera is used, which, for example, may have three sensors (chips) for three different colors, for example, red, green, and blue. By changing the exposure times applicable to the individual sensors in the CCD camera and/or by changing the sensitivity of these individual sensors, the image detected by this CCD camera may be easily changed as a function of time, whereby these changes may be synchronized in a simple manner by scanning the detection space using the light planes that may be arranged one behind the other and may be generated temporally one after the other. Similarly, it may be advantageous to install a rotating filter, for example, in front of each of these chips located in the CCD camera, so as to change as a function of time, in a defined and periodic manner, the intensity detected by these chips.
Furthermore, in place of a CCD color camera it may also be advantageous to use a black/white camera, which may have in its interior, for example, three sensors, whose sensitivity to the intensity of the incident electromagnetic radiation may be changed, in each case separately, as a function of time, so that the sensors each may have assigned to them a false color, for example, red, green, and blue. In this way a color image of the detection space may be obtained from the images recorded by the individual sensors as a function of time, using superposition, for example, carried out in a computer.
In this manner, the two-dimensional image of the detection space finally registered by the image detector may be furnished with color information, which may clearly correlated with the location and time of the generation of a light plane in the detection space and therefore of the y-coordinate of the location of a light-scattering or -emitting particle.
In addition, the image detector(s), during the scanning of the detection space, may be adjusted continuously or step-by-step in their depth of focus, so that in each case an image may be formed of the individual light planes at the location of the image detector at least fairly precisely.